SU442543A1 - Device for group selective protection against current leakage in three-phase electrical networks with insulated neutral - Google Patents

Description

one

This invention relates to current leakage protection devices in three-phase electrical networks with insulated neutral.

The known devices containing a network-wide leakage relay connected to substation buses, leakage blocking relays with a three-phase choke, a sensitive actuating relay installed on the outgoing dipoles, and a source of rectified operating voltage, in series with which the blocking contact of the feeder contactor is connected, are not reliable enough.

In the proposed device for the purpose of gaining reliability, the leakage blocking relays between the zero point of a three-phase throttle and the ground additionally include a series-connected compensating choke and a capacitor, and the source voltage and sensitive actuating relay are connected to the capacitor via a blocking contact of the feeder contactor.

A schematic diagram of the proposed device is shown in the drawing.

A network-wide leakage protection 3 and a contactor 4 are connected to the buses of 1 substation connected to the power source through the automatic switch 2,

5, 6, the control of the feeders A, B, C, on which the blocking leakage relays 7, 8, 9 are installed. The network-wide leakage relay 3 contains a filter connecting the operative to

a controlled network consisting of a three-phase 10, zero chokes, And 12, and a capacitor 13; rectifying bridge 14 for powering operational work; intermediate relay 15 operating in relay mode

with output to the executive relay 16; A U-shaped quadrupole 17, made up of capacitors 18, 19 connected by a resistor 20, allows the device to deform the protective characteristic. Condenser 21

introduced into the network-wide leakage protection device 3 to create a time delay when o-T1 drop and an additional relay 16. To control the contactors 4, 5, 6, feeders A, B, C this relay has open

contacts 22, 23, 24 in the coils of these contactors.

In addition to the relay 16, acting on the feeder contactors 4, 5, 6, this device has another actuating relay 25, contact

26 of which is included in the circuit of the disconnecting coil 27 of the automatic switch 2. This relay performs a protective disconnection of the busbars of the substation and B1 is disconnected, into the operational circuit by the contact 28 16 only when

working out The contacts 29, 30 of the relay 16 are intended for influencing the effect of the capacitor 1y and resistor 2 (j on the conditions of the relay 2o.

Circuit leakage relay relay / contains a filter when connecting the operational dei, consisting of three-phase 5.1, zero 6z chokes and a cici capacitor; rectifying bridge ci4 for feeding the performance value; a relay mode 35 operating in relay mode with an output to the sololitelny relay Sb. For control of contactor 4, this relay has an opening contact 38 in the circuit of the tripping coil, i / of this contactor.

Analog elements and circuit solutions also have a metal rod; p01 vacuum leakage relays and and Y, installed on feeders B and C.

b locking relay leak 1К1И 7; B, blocks: the rotor contact of the charger of the contactor 4 is not connected to the zero droplet circuit 32, but sequentially to the source of operational voltage 34. This inclusion of the blocking charger contact into the leakage blocking relay circuit / makes it possible to use c-e1po: 31, zero 32 chokes and a capacitor 33, to compensate for the capacitive current of the earth fault both with the contactor 4 turned on and after it is turned off. By adjusting the inductance of the filter of the interlocking leakage relay 7 by switching the spikes of zero droplets 32 into resonance with the capacitance of the trunk cables of the feeder 4, the capacitive ground fault current caused by this capacitance is almost fully compensated. Moreover, after disconnection of this feeder, the capacitive current to earth is caused by the emf. the inertia-rotating electric motors are also compensated.

With a similar setting of the filters for interlocking interlocking leakage relays 8 and 9, installed on the feeders B and C, the capacitive earth fault current in the network turns out to be almost fully crumpled, which increases the safety of its operation.

The proposed device monitors the insulation as follows. When a leakage current occurs behind the contacts of the feeder contactor (for example, 4), the amplifier 15, changing its state abruptly, connects the coil of the relay 16 with a parallel connected capacitor 21 to the power supply of the amplifier 15. The capacitance of the capacitor 21 has almost no effect the relay 16 trips, because the resistance of the amplifier 15 is low and the charge of the capacitor 21 is therefore almost instantaneous. The relay 16 is activated and opens its contacts 22, 23, 24 in the coils of the contactors 4, 5, 6. In the result, the feeders A, B, C 01 are faulty. At the same time, the block contacts of contactors 4, o, 6 are closed in the circuit of operational voltages of their own interlocking leakage relays. (this coupling is separately carried out: the role of isolating outgoing feeders A, B, L. Since the leak causing the operation of the osseocontrol leakage protection device 3 separated from it by the contacts of the contactor 4, the amplifier 15 returned to its initial state. It drops out, and some time remains on due to the discharge of the capacitor 21. The time delay must be sufficient to activate the relay 36 and open its contact 38 in the coil 3 / contactor 4 circuit. Turning on this

the contactor will become possible after the insulation resistance of the feeder A is increased to a level at which the amplifier Zo returns to its original state. Nutrition

feeder A is automatically restored.

When the voltage decreases during the discharge of the capacitor 21 to a value when the relay 16 returns to its initial state, the power supply of the intact feeders B and C is automatically restored. The power of the lower driver A can also be automatically restarted, as already mentioned, but subject to an increase in the resistance of its insulation to a defined level.

Relay 1b is also triggered when a trip leak occurs on the substation tires. By opening its contacts 22, 23, 24, it provides the outgoing feeders A, B, C, and the contacts-28, 29, 30 performs the following

operations. The closure of contact 28 includes into the operative circuit of the leakage protection apparatus 3 relays 25 and in order to increase the sensitivity of this relay by opening the contact 29 includes a resistor 20 and a capacitor 19. By closing the contact 30, relay 16 discharges the capacitor prevent the relay 16 from malfunctioning when re-energizing undamaged feeders.

The signal about the occurrence of leakage on the busbars perceives both the relay 16 (through the amplifier 15) and the relay 25. At the same time, the relay 16 prevents the feeders A, B, C from turning on again, and the relay 25 gives contacts 26

impulse to turn off the automatic switch 2.

Subject invention

Device for group selective protection against leakage of current in three-phase electrical networks with insulated neutral, containing a network-wide leakage relay connected to the bus lines, interlocking

three-phase choke leakage relays installed on outgoing feeders, sensitive Auxiliary relay, I1 source of rectified operating voltage, in series with which the switching voltage is connected

Breakout contacting feeder contactor.

characterized in that, in order to increase the reliability of the leakage interlock relays, between the Zero point of the three-phase throttle and the ground are additionally connected in series a connecting choke and a capacitor, and the operating voltage source and sensing actuating relay are connected to the capacitor via a blocking contact of the feeder contactor.